There is a machining device that cuts or pierces a hole in a workpiece using a laser beam (for example, refer to PTL 1 and PTL 2). The machining device disclosed in PTL 1 and PTL 2 cuts or pierces a hole in a workpiece by irradiating the workpiece with a laser beam. A laser beam machining method disclosed in PTL 1 is a method of piercing a hole in a workpiece by irradiating the workpiece with at least two types of wavelength of laser beam, and which includes a step of machining the workpiece by irradiating the workpiece with a first laser beam having a spot diameter smaller than a hole diameter along an inner circumference of a hole, and a step of irradiating a portion inside of the inner circumference of the hole with a second laser beam having a spot diameter smaller than the hole diameter and a wavelength longer than that of the first laser beam, and a part, which remains without being machined in the former step, is machined in the latter step. PTL 1 discloses a device that is configured to offset the irradiation position of the first laser beam via a combination of galvanometer mirrors. PTL 2 discloses a device that is configured to have a coil provided in a structure holding a lens, and a permanent magnet provided in a base, and to rotate the focal point of a laser beam by rotating the lens via the driving of the coil.
PTL 3 filed by the applicant discloses a machining device that includes a CO2 laser beam oscillator and an excimer laser beam oscillator, uses a CO2 laser beam and an excimer laser beam as two laser beams, and cuts or pierces a hole in a plastic member or an FRP member by irradiating the plastic member or the FRP member with the CO2 laser beam, and subsequently, removes a carbonized layer or a heat-affected layer occurring on a cut surface by irradiating the cut surface and the vicinity of the cut surface with the excimer laser beam. In the machining device disclosed in PTL 3, an excimer laser beam having a ring-shaped cross section is generated, the CO2 laser beam is coaxially inserted into a hollow portion of the excimer laser beam, and both the laser beams are transmitted on the same transmission path, are guided to the vicinity of a cutting portion or a pierced hole portion of a plastic member or an FRP member, and both the laser beams are re-separated from each other in the vicinity of the cutting portion or the pierced hole portion.